{
\def\sym#1{\ifmmode^{#1}\else\(^{#1}\)\fi}
\begin{tabular}{l*{2}{c}}
\hline\hline
                    &\multicolumn{1}{c}{\specialcell{\;\;\;\; Arsenic \\ contamination \\ \;\;\;\; (WHO \\ \;\; threshold)}}&\multicolumn{1}{c}{\specialcell{\;\;\;\;\;\; Fecal \\ contamination}}\\\cmidrule(lr){2-2}\cmidrule(lr){3-3}
                    &\multicolumn{1}{c}{(1)}   &\multicolumn{1}{c}{(2)}   \\
\hline
As safe source (baseline) x treated&      -0.021   &      -0.029   \\
                    &     (0.020)   &     (0.032)   \\
Low As Source (baseline) x treated&       0.033   &       0.044   \\
                    &     (0.042)   &     (0.027)   \\
Moderate As Source (baseline) x treated&      -0.044   &       0.052   \\
                    &     (0.046)   &     (0.053)   \\
High As Source (baseline) x treated&      -0.022   &      -0.053   \\
                    &     (0.041)   &     (0.048)   \\
\hline
R$^2$               &        0.10   &        0.04   \\
N                   &        6051   &        6051   \\
\hline\hline
\end{tabular}
}
